1. Field of the Invention
The present invention relates to a supply apparatus for supplying screws or the like each having a shaft and a head portion whose diameter is larger than the shaft (e.g., screw, rivet, or the like; collectively referred to as screws hereinafter), to a predetermined position and, more particularly, relates to a screw supply apparatus having a chute for supplying screws to a predetermined position via a guide slit.
2. Description of the Prior Art
Prior to this application, the present applicant proposed in Japanese Utility Model application No. 60-131054 filed on Aug. 28, 1985 a novel and unique device relating to a screw supply apparatus for supplying screws or the like to a predetermined position through a chute.
According to the device of this prior application, screws charged into a screw storage section are dipped up by a dipper that can oscillate vertically, and the dipped screws are supplied to a predetermined screw supply section through a chute. A guide slit opens on the upper surface of the chute. When screws are supplied to the chute from the dipper, they are supplied to the screw supply section by their weight such that their shafts are inserted in the guide slit and their head portions are engaged with side edge portions of the upper opening of the guide slit.
With this device of the prior application, however, when moisture or dirt exists on the upper surface of the chute, the flow of screws is prevented. In particular, when light-weight screws each having a diameter smaller than 1.4 mm and a length smaller than 3 mm are supplied with the above method using natural dropping of the screws by their own weight, moisture or dirt on the upper surface of the chute greatly affects the flow of the screws on the chute. If the screw flow on the chute is prevented, the screws are not smoothly supplied to the screw supply section, and an operation for mounting screws becomes very inefficient.
In order to eliminate the above drawback, a method is proposed wherein the chute is continuously vibrated by an electromagnet or the like, thereby allowing a smooth flow of screws on the chute. When the chute is continuously vibrated, however, a screw cannot be easily taken out from the screw supply section of the chute. More particularly, when screws are taken out from the screw supply section by attracting their head portions magnetically with a magnetic screwdriver, a screw attracted by the magnetic screwdriver can be dropped unexpectedly therefrom by the above noted vibration, and the screw removal operation becomes difficult.